Manufacture of electric-furnace linings



July 17, 1923.

, W. R. CLARK MANUFACTURE OF ELECTRIC FURNACE LININGS Filed Aug. 6, 1917 Hill IIHI

Patented July 17, 1923.

UNITED STATES 4 1,461,862 PATENT OFFICE.

WALTER R. CLARK, OF BRIDGEPOBT, CONNECTICUT, ASSIGNOR TO BRIDGEPOR'I BRASS COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPORATION OF CONNECTICUT.

MANUFACTURE.OF ELECTRIC-FURNACE LININGS.

Application filed August 6, 1917.

To all whom it may concern Be it known that I, \VALTER R. CLARK, a citizen of the United States, .residing in Bridgeport, in the county of Fairlield and 'State of Connecticut, have invented certain new and useful Improvements in the Mannfacture of Electric-Furnace Linings, of which the following is a full, clear, and exact description. 4

This invention relates to the manufacture of electric furnace linings, and more particularly the linings of induction furnaces of the type in which a. tube or passage of closed cross-section, communicating with the hearth at two points, receives a portion of the molten bath, which acts as the secondary of the transformer. The molten metal is circulated through the secondary passage or channel by motor effect, thereby establishinga circulation of the bath and transmitting the heat to all portions thereof. The channel, tube'or passage through which the metal of the secondary flows is usually formed of, or lined with a suitable material which will satisfactorily withstand the high temperature developed.

.In furnaces .of the type mentioned, especially where the secondary is of rather small cross-section, itis very diflicult to form the refractory portion having, or associated with, the secondary passage, channel or duct, in such a way that the wall of the passage or duct will be perfectly homogeneous, and at the same time, sufficiently smooth, and uniform in cross-section, for proper furnac'e operation. One of the methods heretofore used inmaking the refractory structure having the secondary passage, chan- .nel, duct or bore was to ram up a furnace lining around a casting composed of an alloy of the materials which were to be melted in the furnace later on. Such an alloy casting is of the same cross-sectional area and shape'as thedesired secondary channel of introduced into the furnace in the molten Serial No. 184,675.

state to increase the volume of the molten bath, so that it will act as a bed for receiving the first charge to be melted. In this way, the pattern is utilized to create a portion. of the bath when the completed furnace' is first placed in operation.

In furnaces constructedin this manner, especially when used for melting materials having fairly high melting points, for example, brass scraps or turnings, the expansion of the metal pattern or templet which is incident to heating it to the melting point, is considerable, because in such case, the pattern or templet is made of the same material, e. g., brass, which is to be melted in the furnace. Owing to the shape of the pattern, its considerable expansion prior to melting, creates great pressure upon the surrounding lining, which usually has a dif-' ferent coefficient of expansion. This pressure is so great as to frequently cause'small cracks or fissures to appear in the refractory lining, which will cause the same to have a very short life, sometimes causing failure of the furnace from the start, due to the leakage I of the molten metal through these cracks or fissures. ,Tllis destructive pressure of the pattern may be exerted in a lateral direction relatively to the secondary channel, or in a longitudinal direction relatively thereto, or in both directions, or in any one or more oblique directions. Of course the longitudinally exerted pressure is detrimental owing t the very close fric tion'al contact between the pattern and the lining. During the preliminary heating operation, the stress put upon the pattern is sometimes sufficient to cause a complete rupture of the same, thereby creating a gap in the secondary circuit, which it is impossible to close, making it necessary to pull down and rebuild the furnace. Such rupture of the melting of brass because a brass-pattern will often become more'or less brittle at some temperature between the ordinary .the pattern is especially liable to occur in atmospheric temperature and the ordinary' melting point, depending upon the composition thereof; and under such conditions the lengthening or extension of the patthis procedure is very slow and unsatisfacming and drying operation is completed, but

tory, and it is very difiicult to removethe wood entirely from any sharp corners of the secondary passage should the, latter be made with one or more sharp turns, as is frequently the case.

The primary object of my present invention is to obviate the above mentioned difficulties and to facilitate the manufacture of induction furnaces of the type above described. Another object of the invention is the provision of a pattern for the purpose indicated,.which neither injuriously affects the lining of the furnace, nor themetal 01' alloys which the furnace is intended to melt, which pattern is hard enough and strong enough at ordinary temperatures to allow .the refractory to be rammed about it in a satisfactory way, but which, nevertheless, does not exert injurious pressure on the lining during the preliminary melting.

0 these and other ends, the invention consists in the novel features and procedure hereinafter described and claimed.

In the accompanying drawing, Fig. 1 is a vertical central section of an induction furnace, showing the same in the process of construction, with a reenforced wax templet or pattern in the secondary channel;

Fig. 2 is a detail of the templet or pattern shown in Fig. 1;

Fig. 3 is a side elevation of the templet; Fig. 4' is a section on line 4-4 of Fig. l;

and

' nel of approximately V-shape, indicated at" Fig. 5 is a cross-section of another templet which may be employed.

In the drawing, I have shown an electric induction fzurnace having a body 10, composedpf a metal jacket or casing 11, and a refractory lining 14. The furnace has a basin or hearth 13 at the upper part, which in this case is formed in a layer or body ofrefractory material packed within a layer.

12 of suitable heat insulating material, such for example as infusorial earth. The layer 14 advantageously consists of a suitable asbestos cement, although I do not limit myself in this respect. The hearth has a pour-. .ing spout 15, and a charging opening 16,

having a door 17. Beneath the hearth of the furnace shown herein is a closed chan- 18, having substantially straight side portions communicatlng with each other at an acute angle, as shown at 19,-and connecting with the hearth at opposite sides of the latter, as shown at 20. he metal which is received irijthe channel 18 in the operation of the furnace acts as a secondary of a transformer whose primary is constituted by a horizontally arranged core 21 extending about the upperportion of the channel '18 and having a winding 21" suitably connected with asource of current. Owing to the arrangement of the two legs of the channel '18 at an, acute angle to each other, the

action of the primary is such as to set up, a

thorough circulation of molten metal in the channel and the bath or pool in the hearth, it being understood, of course, that in practice the upper ends of the continuous channel are in constant communication with the lower part of the hearth which is filled to approximately the level of the pouring spout with a bath of molten metal.

In constructing the lower portion of a furnace such as that selected for illustration, I use a. pattern or templet 22 for forming the channel 18 in the refractory mate rial. This pattern or templet. 22 is of the same shape as the passage or channel, which it is desired to form, and in the embodiment shown in Figs. 1-4, it consists of a body 23 of a parafiine, or other hydrocarbon or the like, in which'is-embedded a metallic core 24 which may advantageously consist of woven copper wire in the form of a sheet which is embedded in the center of the par: affine. This pattern or templet 22 is held in position in a suitable frame, and the refractory material, such as asbestos, cement, in

into and fill the minute voids of the lining or to flow outof the channel, Or, if desired, the refractory material can be dried electrically by passing an electric current through the metallic core 24, which melts the paraffine and usually drives it into the I lining, at the sameftime that the heat generated by the current dries out the lining.

In drying out thelining electrically the ends of the metal portion of the templet may be connected to the poles of an exterior source of current, or the transformer =may be utilized ifthe metal portion of the templet is suitably short circuited so that it Will form a closed circuit, for example, by interconnecting the ends of the. metal with a piece of wire. This wire is removed after the furnace has dried, for, in starting the furnace, molten metal poured intothe hearth will complete the secondary inan obvious manner. The parafiinc has no deleterious effect upon the lining nor upon the metal or alloys which are to bemelted. The driving of the solid hydrocarbon into the voids of the lining is a feature of adwould lnjuriously affect it. 40

tallic reticulated or forainmous material remains in the channel after the paraffine has been eliminated. and the radiation of heat from the metallic conductor therein can then be continued by maintaining the electrical connections, so as to thoroughly dry out said passage. The metal portion of the pattern may also remain in the channel when the furnace is placed in operation, inasmuch 'as it will, if made of suitable material, alloy properly with the material to be melted in the furnace. example, is to be melted in the furnace, the reticulated core of the pattern may either be made of brass or copper.-

It is important to note that in starting the furnace after'the parafiine has been driven out of the channel and the refractory has been properly dried, the metal remnant of the pattern is not in tight contact with the wall of the channel. By making the core of suitable reticulated material, it is extensible to a considerable degree without breaking, and even if a fairly high temperature is necessary to melt it, it will not rupture before melting, and

' therefore the secondary is not likely to be broken or"interrupted. The metallic core or other remnant, in expanding, does not exert on the lining any such pressure as I consider it most advantageous to make the metallic core of a fabric woven from copper wire, as cop-per is ductile at all temperatures up to melting, and in case the furnace is started on brass (with molten brass poured in around the core), and the brass tends to solidify in the secondarypassage, the duetility of the wire will usually prevent effectively a complete or harmful rupture of the secondary.

If, under certain circumstances, it is desined to prevent the paraffine from being dr ven into the lining material, when the former is melted, the parafiine templet may be coated on the outside with shellac or varnish of high melting point. This will enable the melted parafiine to be poured out of the channel without going into the lining.

In other cases, I may use a pattern comprising a very thin metal tube of the metal which is to be melted in the furnace, the said tube being filled with wax, sand, or other suitable substance, which reenforces it interiorly to such an extent as .to offer sufficient resistance to ramming. In Fig.

l, I have shown in cross-section a thin metal.

If brass, for

tube 25, which may be of copper, for example, and in the tube is a filling 26 of sand, which. prevents the tube from collapsing when the refractory material is rammed about it. When the operation (if-ramming is completed, the sand can be run out of the tube very readily, as will be understood.

in heating up the refractory structure, cither for drying it or in starting the furnace, and either by the application of external heat, or by the use of an electric cur rent passing through the metallic tubular core, the tube will collapse inwardly in a lateral direction under the expanding infiuence of the heat instead of expanding laterally in an outward direction, or extending itself lengthwise, and hence there will be no severe lateral and outward pressure, or oblique pressure, or longitudinal pressure on the lining, or, at any rate, not sufficient pressure in any of those directions to crack the lining or affect it injuriously. If the tubular pattern is filled. with wax, for example, the wax can be quickly eliminated by passing a current through the tube, which is thereby permitted to collapse inwardly. In otherwords, as the wax is quickly eliminated, it offers no appreciable resistance to the inward collapse of the tube, and outward in substantially the same manner as the other metallic templet remnant hereinbefore described.

A tube such as that shown in Fig. 5, may not only be made of copper or other metal of low melting point, but it may be made of metals having a high melting point, such as platinum, tungsten alloy, or nickel chrome alloy, where certain materials are to be melted in the furnace. Tubesof high melting point will hardly be used, however, except in rather exceptional cases.

Various changes may be made in the procedure and apparatus herein particularly described without departing from the scope of my invention as defined in the claims.

I'do not claim specifically herein a templet for the manufacture of electric induction furnaces and the like: having an interior filling of readily meltable material, as claimed in my divisional application Serial No. 322.556.

What I claim is '1. The method of making the refractory structure of an electric furnace or the like having an interior passage or channel, which comprises tamping refractory material about a pattern of the same shape as the passage to be formed, made at least partly of a nonmetallic material which at ordinary temperatures is suficiently hard and strong to resist collapse under the tamping pressure, but Which melts at a low temperature, and applying heat to the structure for removing such non-metallic material from the passage, and drying the structure.

2. The method of making the refractory structure of an electric induction furnace having a passage of closed cross-section arranged beneath and in communication with the hearth or basin thereof, which comprises tamping refractory material on all sides but not at the ends about apatternof the same shape as the passage to be formed, and which ismade at least partlyof a pliable, readily meltable, non-metallic solid which -is sufliciently hard and strong to resist distortion under the proper tamping pressure, and then melting such material by the application of heat.

3. The method of making the refractory structure of an electric induction furnace having a passage of closed cross-section arranged beneath and in communication with the hearth or basin thereof, which comprises tamping refractory material at different sides but not at the ends about a pattern of the same shape as the passage to be formed and which is made at least partly of a pliable, readily meltable, non-metallic solid which is sufliciently hard and strong to resist distortion under the proper tamping pressure, then melting such material bythe application of heat and running ofi'a portion of the same from the passage ends, and continuing the application of heat after the melting of such material to dry the refractory material thoroughly.

4. The method of making the refractory structure of an electric furnace -or the 'like having an interior passage, whichcomprises tamping the refractory materiah about a pattern or templet which consists partly of a metal conductor and partly of a body of material of a lower melting point than said conductor, melting and thereby eliminating the low melting point portion. of the pattern after the tamping operation has been completed, and then drying the structure while the metallic conductor portion of the pattern remains in place.-

- 5. The method of making the refractory structure of an electric furnace or the like having an interior passage of closed crosssection, which comprises tamping the refrac- -,tory material about a pattern or templet which is made partly of metal of high melting point and partly of a body of low melting point, eliminating the low melting point portion of the pattern by melting after the tamping operation has been completed, and then drying the structure.

6. The method of making the refractory structure of an electric'induction furnace having a passage of closed cross-section arranged beneath and in communication at both ends with the hearth or basin thereof, which comprises tamping plastic refractory material on all sides of a pattern of the same shape as the passage to be formed, but leaving such pattern free at the ends, such pattern'consisting at least partly of a pliable, readily meltable solid, then melting such material so that a portion thereof is absorbed by the lining of the passage and then carbonizing the material so absorbed by the lining.

7. The method of making a refractory structure of an electric induction furnace having a secondary passage, which comprises supporting in a suitable frame, a pattern of the same shape as the secondary passage to be formed, such pattern consisting at least partly of a non-metallic material which at ordinary temperatures is sufiiciently hard to resist collapse under tamping pressure but which melts at a low temperature, tamping refractory material in plastic condition about the sides of such pattern, but leaving the same free at one or more points to permit the escape of the melted material, applying heat to the structure for melting and eliminating such material, and continuing the heating of the structure so' asto dry the same and carbonize any of the pattern material absorbed in the lining of the passage.

8.'The method of making an electric induction furnace and placing it in operation, which comprises ramming, refractory material about a pattern composed partly of metal and partly of a substance of low melting point, eliminating by melting the low-melting pointsubstance and drying the furnace structure, passing an electric current through the metallic remnant of the pattern when the furnace is to be placed in operation, and pouring into the furnace molten metal which makes contact with the metallic remnant of the pattern while the current traverses the latter.

9. The method of lining the hearths of electric'induction furnaces, which comprises placing the lining material around a templet consisting partly of metal and partly of a thick coherent non-metallic unitary body oflow melting point which is sufficientlyhard to withstand the ramming pressure at ordinary temperatures, eliminating by melting the non-metallic body after the lining material has been tam'ped in place, pouring molten metal into the furnace around the remnant of the templet, and passing electric current through such metallic remnant, for starting the furnace. I i

10. The method of making the refractory structure of an electric induction furnace, which comprises ramming refractory material around a templet composed partly of wax and partly of metal, heating the wax to melt and eliminate the same, pouring molten'metal into contact with the metallic remnant of the templet, and passing electric current through such metallic remnant, for starting the furnace.

11. The method of making the refractory structure of an electric induction furnace having a secondary passage of closed crosssection arranged beneath and in communication with the hearth or basin thereof, which comprises tamping refractory material on all sides, but not-at the ends, about a pattern of the same shape as the passage to be formed and which consists partly of metal and partly of non-metallic material of low melting point, eliminating the nonmetallic portion of the pattern by melting the same after the tamping operation has been completed, and then drying the structure while the metallic portion of the pattern remains in place.

12. The method of making and operating an electric induction furnace having a secondary passage of closed cross-section ar ranged-beneath and in communication with the hearth or basin thereof, which comprises tamping refractory material on all sides, but not at the ends, about a pattern of the same shape as the passage to be formed, which pattern consists partly of non-metallic material of low melting oint and partly of an interior metal rein orce, melting and thereby eliminating the nonmetallic portion of the pattern after the tamping operation has been completed, and operating the furnacewhile the metallic portion of the pattern remains in place in the passage.

13. The method of making an electric induction furnace having a hearth with a heating passage connected therewith, which comprises ramming refractory material about a templet of the same shape as the passage to be formed, said templet consisting of a readily meltable non-metallic body having a metallic core extending from one end of the templet to the other, eliminating the nonmetallic component of the templet by the application of heat, passing an electric current through the core after the non-metallic component has been eliminated, and starting the furnace while such electric current traverses the core. Y

14. The method of constructing and operating an electric induct ion furnace having a hearth or chamber with a secondary passage of closed cross-section connected therewith, which comprises ramming suitable plastic material about a templet of the same shape as the passage to be formed, said templet consisting partly of metal and partly of a nonmetallic substance of low melting point, then eliminating by melting the non-metallic portion of the templet, and meltin the metallic remnant of the templet when t e furnace is to be started.

15. The method of constructing and operating an electric induction furnace havin a chamber with a secondary passage of closed cross-section connected therewith,

which comprises ramming a suitable plastic material about a templet of the same shape as the passage tobe formed, and consisting partly of metal and partly of a readily meltable non-metallic substance, applying heat to the structure for melting and eliminating the non-metallic component of the templet, inducing an electric current in the metallic remnant of the templet to melt the same in said passage, and placing additional metal in the furnace chamber to complete the charge.

16. The method of constructing and operating an electric induction furnace having a secondary passage, which comprises ramming a suitable plastic material about a templet of the same shape as the passage to be formed, said templet consisting partly of a metal conductor and partly of material of lower melting point than said conductor, melting out the material of lower melting point, and melting the metallic conductor portion of the templet in said passage when the operation ofthe furnace is commenced.

17 The method of making and operating an electric induction furnace having a secondary passage, which comprises tamping about a pattern or templet of the same shape as the secondary passage to be formed, refractory material, such pattern or templet consisting of a metallic inner part and a readily ,meltable non-metallic outer part, melting the non-metallic outer part of the pattern to eliminate the same after the tamping operation has been completed, and starting the furnace while the metallic portion of the pattern remains in place in the secondary passage.

18. In the manufacture of an electric induction furnace having a refractory structure with a secondary passage therein, increasing the density of the lining of such passage by treatment with a non-metallic material which closes the pores of the refractory.

l9.- In the manufacture of an electric induct-ion furnace having a refractory structure witha secondary passage therein, the step of treating the lining of the passage with a hydrocarbon.

20. lln the manufacture of an electric induction furnace having a refractory structure with a secondary passage therein, treating the lining of the secondary assage with material containing a hydrocarbon, and then carbonizing such material, whereby the density of the lining is increased.

21. In the manufacture of a refractory furnace structure having an interior passage, driving a waxy substance into the liniiig of the passage by the application of heat.

22. The method of making the refractory structure of an electric furnace having an interior passage, whichcomprises tamping the refractory material abouta pattern or templet, which consists of an outer waxy body of considerable bulk and an inner flexible metallic conductor, melting the waxy portion of the'pattern so as to drive at least a part of the waxy material into the lining of the passage to thereby improve the same, and drying the structure while the metallic portion of the pattern remains in place.

23. In the manufactureof a refractory furnace. structure, the step of filling up the voids in the refractory by treatment with a waxy substance.

24. In the manufacture of a refractory furnace structure, the step of filling up the voids in the refractory by treatment with a waxy substance, which is subsequently carbonized.

25. A templet for the purpose described consisting partly of wax and partly of a flexible copper reinforce embedded in the wax and extending out of the same at both ends of the templet.

26. A templet for the purpose described, consisting-partly of wax and partly of a longitudinal reinforce embedded in the wax,

such reinforce comprising one or more strands of ductile metal.

27. A templet for the purpose described, which comprises a wax-like body having a reticulated flexible reenforce embedded therein and extending longitudinally therethrough.

28. A templet such.as described having a metallic core extending longitudinally therethrough.

29. A templet for the purpose described, having a reticulated copper core embedded therein and extending therethrough.

30. The method of starting an induction furnace, which consists in placing within the heating space of said furnace a compositebody formed of materials of different melting points, then melting the material of lower melting point, and then melting the material of higher melting point.

31. The method of starting an induction furnace, which consists in placing .with the heating space of said furnace a composite body formed of materials of different melting points, then melting the material of lower melting point, and then melting the material of higher melting point by induction.

32. The method of starting an induction furnace, which consists in placing within the heating space of said furnace fusible materials of different melting points respectively, then melting the material of lower melting point, and finally melting the prises placing within the furnace space a com osite body formed of materials of high and ow melting points respectively, melting the low melting point portion of the body,

drying the structure, and then utilizing the high'melting point portion of the body for starting the furnace, by inducinga currenttherein.

34. The method of making and operating an induction furnace, which comprises placing'in a refractory furnace structure a composite body having portions. of different melting points adapted for successive melting in placing the furnace in operation, so as to minimize the lateral pressure on the refractory wall.

35. The method of making an electric furnace, which comprises building a refractory structure about a composite templet composed of a conductor portion of high melting point and a portion of low melting point, one of said templet portions being located at a substantial distance from the lateral walls of the refractory structure,

and inducing a current in the templet to fuse the portion of lowmelting point.

36. The method of drying a green refractory structure, which comprises the location of a composite electric conductor within but at a substantial distance from the lateral walls of the refractory body, and the induction of current in said conductor, whereby the pressure on such lateral walls is minimized.

37. The method of making an electric furnace, which comprises building a refractory structure about a composite conductor templet composed of a portion of high melting point and a surrounding thick unitary body of low melting point, inducing a current in the templet to fuse and eliminate the portion of low melting point, and con- 'tinuing the induction for drying out the furnace.

38. The method of making an electric furnace, which comprises building a refractory structure about a composite conductor templet composed of a portion of high melting point and a thick solid body of low melting point, inducing a current in the term plet to fuse and eliminate the portion of low melting point, and continuing the in duction for drying out the furnace, and finally, melting'the portion of high melting point for'starting the furnace.

In witness whereof, T have hereunto set my hand, on the 2nd day of August, 1917.

WALTER R. CLARK. 

